Thread break detector



y 1969 A. B. CAUSBY ET AL 3,442,237

THREAD BREAK DETECTQR Filed April 7, 1967 and CLARENCE \MMINTON ATTORNEY-S United States Patent 3,442,237 THREAD BREAK DETECTOR Arthur Bennett Causby, Valdese, N.C., and Clarence W.

Minton, Nashville, Tenn., assignors to Stevens Hosiery Division of .l. P. Stevens & C0,, Hickory, N.C., a

corporation of Delaware Filed Apr. 7, 1967, Ser. No. 629,246 Int. Cl. Dh 51/00 US. Cl. 112218 6 Claims ABSTRACT OF THE DISCLOSURE The present invention relates to a thread break detector and more particularly to such a detector which is operable with one or more sewing threads and which provides improved detection of thread breakage or undue slackening.

Thread break detection devices heretofore utilized with sewing machines have suffered from one or both of two major deficiencies. Firstly, one type of prior thread break detection devices have been usable with only a single sewing thread, and, if the sewing machine requires more than one thread, a multiplicity of the devices have been required. Other devices, while being capable of operating with a plurality of sewing threads, have nevertheless been complex in construction and required separate contact switch elements for each sewing thread passing through the detector. With both of these types of devices, substantial duplication of parts resulting in increased cost and maintenance have limited the usefulness and operability.

Another major deficiency which has characterized all of the prior thread break detecting devices with which we are familiar is that the thread sensing members are exposed and therefore are susceptible to the collection of lint or other waste material thereon. This accumulated material frequently impedes the passage of thread through the devices and interferes with the proper operation thereof. Also, the thread sensing members are susceptible to becoming damaged by accidental striking thereof in the operation and/ or cleaning and maintenance of the sewing machines.

The mounting of such devices on or near the sewing machines so as to be in the path of sewing threads from their source to the operating instrumentalities of the sewing machine has heretofore been another problem, and various and sundry mounting arrangements have been proposed. However, none of these mounting arrangements have been entirely successful since they all require either modification or permanent distortion of the sewing machine housing or a substantial change in the path of sewing thread travel from the source to the operating instrumentalities.

It is therefore an object of the present invention to provide a thread break detection device which obviates the aforementioned deficiencies of thread break detection devices heretofore employed.

A more specific object of the present invention is to provide a thread break detection device of the character described having thread sensing means protected against 3,442,237 Patented May 6, 1969 the accumulation of waste material thereon or damage thereto by accidents occuring during the operation and/or maintenance of the machines.

Another object of the present invention is to provide a thread break detection device which is compact in construction and arrangement and is simple in construction so as to be inexpensive and relatively free from maintenance problems and so as to be easily added to or removed from a sewing machine as a sub-unit without modification of the sewing machine or a material change in the path of sewing thread travel. 1

A more specific object of the present invention is to provide a thread break detection device "which is capable of operating with a plurality of sewing threads Without any unnecessary duplication of elements.

Some of the objects of the invention having been stated, other objects will appear as the description proceeds when taken in connection with the accompanying drawings in which- FIGURE 1 is an isometric view of a sewing machine having the thread break detection device of the present invention mounted thereon;

FIGURE 2 is an enlarged fragmentary elevational view of the thread break detection device of the present invention looking in the direction of the arrow 2 in FIG- URE 1;

FIGURE 3 is a sectional view taken substantially along line 3-3 in FIGURE 2; and

FIGURE 4 is an exploded isometric view of the thread break sensing means shown in the left-hand portion of FIGURE 2.

Referring now more specifically to the drawings and particularly to FIGURE 1, there is shown therein a sewing machine 10 which is exemplary of the sewing machines with which thread detection device 11 of the present invention is usable. Sewing machine 10 may be of any conventional character employing single or multiple sewing threads, but as illustrated in the drawings, sewing machine 10 is of the overedge seaming type employing three sewing threads, T T and T In view of the conventional character of sewing machine 10, it is deemed unnecessary to specifically describe the same herein.

Thread break detection device 11 of the present invention is preferably constructed so as to constitute a subassembly for sewing machine 10 for ease in mounting the same in any desired position relative to the sewing machine without permanent modification of the sewing machine or substantial distortion of the path of travel of the sewing threads and for ease in construction and maintenance thereof. To this end, thread break detection device 11 includes a standard 12 adapted to be mounted on the sewing machine or support therefor at any convenient location. A base member 13 (FIGURE 2) is mounted on standard 12 and is preferably formed of a single piece of material of any desired character but preferably lightweight, cast aluminum. Base member 13 includes at one end thereof an upstanding boss portion 14 having a vertically extending opening 15 therethrough. A signal means 16 which preferably is in the form of a light, is mounted in the opening 15 in boss portion 14.

At an intermediate point thereon, base 13 includes a second upstanding boss 17 which has a generally horizontally extending opening 18 therethrough. A microswitch 20 is mounted on base 13 by a suitable bolt or other fastening means 21 which penetrates through opening 18 in second boss 17. Microswitch 20 is connected to signal means 16 by a pair of wires 22, 23 and includes a suitable actuating element 24 which extends outwardly therefrom above and generally parallel to base 13. Actuating element 24 includes a spring portion 24a which biases the actuating element upwardly and serves to normally maintain the switch 20 open, but actuating element 24 will close switch 20 when moved downwardly toward base 13. To this end, switch 20 includes a pair of spaced apart contacts 25, 26, with contact 26 being connected to wire 22 but contact 25 being an open contact or one which is not connected to any electrical circuit or to ground. A movable switch element 27 is connected at one end to wire 23 and at its other end to the actuating element 24 for movement between the spaced-apart contacts 25, 26.

A thread break sensing means 30 is mounted on the opposite end of base 13 from the first boss portion 14 and includes a housing 31. Housing 31 includes a main portion 32 and a cover portion 33. Main portion 32 of housing 31 is mounted on base portion 12 by a depending flange 34 which fits into a mating cutout in the side edge portion of base 13. A pair of screws 35 penetrate through suitable openings 36 in flange portion 34 and into internally threaded openings 37 in base 13. Cover portion 33 is mounted on main portion 32 by suitable bolts 38 (FIG- URE 4).

Main portion 32 of housing 31 has a vertically extending elongate opening 40 therethrough which extends from a point adjacent to but spaced slightly above base 13 upwardly to the top surface of the main portion 32 and serves to divide main portion 32 in portions 32a, 32b. The actuating element 24 of switch means 20 penetrates through opening 40 in housing body portion 32 at an intermediate point therein.

Portions 32a, 32b of main portion 32 of housing 31 on opposite sides of opening 40 include at least one pair of vertically extending grooves 41, 42 therein. The groove 42 extends through portion 32b of the main portion and is closed by cover portion 33 whereas groove 41 is of less depth than the thickness of portion 32a. Also, the grooves 41, 42 are closed at their tops and bottoms and are of a predetermined width.

Preferably, a plurality of pairs of such grooves 41, 42 are provided corresponding to the number of sewing threads used by the sewing machine. As illustrated, three such pairs of grooves are shown in the housing 31 since the sewing machine utilizes three sewing threads.

Main portion 32 and cover portion 33 respectively have transversely extending aligned eyelet openings 43, 44 for each pair of grooves 41, 42 adjacent the tops of the grooves and communicating therewith. These eyelet openings are adapted to pass sewing threads T T and T laterally through the housing. Preferably, the series of eyelet openings 43, 44 are inclined relative to base 13 at an angle corresponding to the angle which the actuating element 24 of switch 20 normally occupies when the threads T T and T are passing through the housing in normal operating manner (FIGURE 2).

A weighted thread sensing member 50, preferably of generally cylindrical shape, is mounted in each pair of grooves 41, '42. Preferably, members 50 have opposite end portions of a diameter substantially corresponding to the width of the grooves so that the same substantially fill the grooves. Each of the weighted members 50 has an axially extending opening 51 therethrough which is adapted to receive and pass a corresponding one of the sewing threads T T T therethrough so that the sensing member is normally supported thereby and is maintained adjacent the top of the pair of grooves 41, 42 or in substantial horizontal alignment with the eyelet openings.43, 44. Each weighted thread sensing member also preferably includes a medially disposed circumferentital groove 52 which is generally disposed within the opening 40 in housing 31 above the switch actuating element 24 so that the actuating element will be received therewithin upon engagement between the weighted thread sensing member 50 and the actuating element. It is noted that because of the inclined arrangement of the series of eyelet openings, the weighted sensing members 50 are all supported by the sewing threads at substantially the same distance above actuating element 24. This insures that each member 50 must travel the same distance before striking actuating element 24 and, therefore, permits the same degree of slackness in any of the sewing threads before switch 20 is actuated.

In operation, the thread sensing members 50 corresponding to the number of sewing threads to be utilized with the sewing machine are placed within grooves 41, 42 in the housing 31 and the sewing threads T T and T are threaded through the eyelet openings 43 and 44 and through the corresonding thread sensing members 50. These threads, during their normal opepration with the sewing machine 10, support the weighted thread sensing members above the actuating element 24 so that switch means 20 remains in an un actuated or open condition. By being enclosed within the grooves 41, 42 and housing 31, the weighted thread sensing members are not susceptible to the collection of foreign matter, such as lint and waste, thereon and therefore remain free for movement up and down within grooves 41, 42 depending upon the tension in the threads T T or T If one or more of the threads become unduly slackened or broken, the weighted sensing member or members corresponding thereto move downwardly under the influence of gravity into contact with the switch actuating element 24 and will depress the same. This moves element 27 of switch 20 from contact 25 into engagement with contact 26 which completes an electric circuit therethrough to the signal means 16. A signal is therefore given to the operator of the machine that the sewing thread is broken or unduly slackened. Any one or combination of the weighted thread sensing members 50 will actuate the switch means 20 and therefore a single switch means and signal means is required for a sewing machine regardless of the number of sewing threads being utilized therewith.

It is therefore believed apparent that the present invention provides an improved thread break detection device in which the sensing means is enclosed within a protective housing and is therefore protected against malfunction due to the collection of waste material thereon or damage due to maintenance or operation of the machine and wherein undue duplication of elements is obviated.

In the drawings and specification there has been set forth a preferred embodiment of the invention, and although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation.

' We claim:

1. A thread break detector for a sewing machine comprising (a) a housing having a substantially vertically extending, elongate open-ing therethrough, said housing having at least one pair of opposed, vertical grooves closed at their tops and bottoms and disposed one on each side of said opening in facing, aligned relationship, said housing also having a pair of horizontally disposed, aligned eyelet openings communicating with the top portions of said grooves and adapted to pass a thread therethrough laterally through said housing,

(b) a weighted thread sensing member having opposite end portions thereof disposed in said grooves and of a width substantially the same as the width of said grooves, said thread sensing member extending across said elongate opening in said housing and having an opening therethrough parallel to said eyelet openings in said housing and adapted to receive the thread passing through said eyelet openings therein, said sensing member beng adapted to be supported adjacent the top of said grooves by the thread when the same has a predetermined tension therein and to move downwardly by gravity when not supported thereby as when the thread breaks or becomes unduly slackened, and

(c) switch means having an upwardly biased actuating element extending through said elongate opening in said housing beneath said thread sensing member and 5 adapted to be moved downwardly thereby to actuate said switch means.

2. A thread break detector according to claim 1 wherein said weighted thread sensing member is cylindrical and is rotatively mounted in said grooves.

3. A thread break detector according to claim 1 wherein said housing has a plurality of pairs of grooves and eyelet openings, and including a plurality of weighted thread sensing members'disposed one in each pair of grooves and all disposed above said actuating element of said switch means.

4-. In an apparatus according to claim 3 wherein said sewing machine is a multiple thread sewing machine and wherein said actauting element of said thread detector normally occupies an upwardly inclined position at an acute angle to the horizontal and said plurality of eyelet openings are arranged in an inclined row at a corresponding acute angle to the horizontal so that said thread sensing members will normally be supported by the sewing threads at substantially the same distance above said actuating element.

5. A thread break detector according to claim 1 including (d) signal means connected to said switch means and 6 actuatable thereby to signal a machine operator that the sewing thread has broken or become unduly slackened.

6. A thread break detector according to claim 5 including (e) a unitary base mounting said housing, said switch means and said signal means as a compact sub-unit for ease in mounting the same on or in association with a sewing machine.

References Cited UNITED STATES PATENTS 2,400,529 5/1946 Behrens 112219 2,825,119 3/1958 Heffelfinger et a1 28-51 3,159,123 12/1964 Godwin et al. 20061.18 XR FOREIGN PATENTS 900,680 12/ 1953 Germany.

H. HAMPTON HUNTER, Primary Examiner.

US. Cl. X.R. 

